This application is related to U.S. patent application Ser. No. 371,546, entitled Hardware For Panel Doors, filed Apr. 26, 1982, by Torsti T. T. Jerila. The subject matter of the application is hereby incorporated by reference.
A type of door that has become increasingly popular, particularly for closets and the like, is a so-called bifold door. In a typical opening, four door panels are used. Two of these panels are hinged together at each side of the opening. The panel nearer the jamb (referred to herein as the pivot door) may be pivoted at the top and bottom to support the full weight of both doors. The other panel further from the frame (referred to herein as the lead door) typically has guides at the top and bottom which run in a track to keep the edge of the door within the frame.
Thus, when the doors are closed both doors are in the plane of the frame. To open a pair of doors one pulls at the hinge line, causing the doors to "fold" relative to each other. As the doors open, the pivot door pivots adjacent the jamb and the hinge edge of the lead door swings outwardly as constrained by the hinges between the doors and the guides in the tracks.
A popular type of bifold door has a flat rectangular panel which may be a mirror, plywood, pressed board, or the like. A metal stile fits on each edge of the panel and a metal rail is positioned at the top and at the bottom of the panel. The stiles and rails are connected together at the corners of the panel by corner connectors or corner blocks which are typically connected to the stile and rail rather than to the panel. A pair of pivots may be inserted into a hole in each of a pair of the corner blocks on the pivot door and a pair of guides may be inserted into holes in a pair of the corner blocks on the lead door. Such an arrangement is described and illustrated in the aforementioned patent application.
Quite often one closes such a pair of bifold doors by pressing laterally on the doors at the hinge line. When the doors are properly mounted, such pressure will cause the guide on the lead door to move away from the jamb toward the closed position. To close solely by application of pressure at the hinge line, the doors should be mounted so that the lead door never moves to a position perpendicular to the plane of the frame. In fact, to operate properly the angle between the fully open lead door and track should be appreciably less than ninety degrees. One way of assuring that the lead door has adequate "lead-off" to close properly when the door is open is to connect the guide to a sliding spacer or to place a blocking spacer at the pivot to hold the edges of the doors apart. Thus, instead of the two doors meeting to be substantially parallel with each other, the edges are held apart so that the two door panels form a sharp V. This leaves the lead door with enough of an angle that lateral pressure at the hinge line will cause the doors to close.
This arrangement is not the most desirable for at least a couple of reasons. The additional spacers at the top and bottom are an element of cost that is preferably avoided. Further, by holding the doors apart, the pivot door is also prevented from reaching ninety degrees relative to the track and the effective width of the opening is noticeably reduced.
When wood frame doors or the like are used to make a bifold set, lead-off can be provided by placing the pivots a somewhat greater distance from the edge of the pivot door than the guides are placed from the edge of the lead door. As such a set of doors opens, the pivot door may swing through more than ninety degrees out of the plane of the frame, leaving the lead door at enough of an angle relative to the track that pressure at the hinge line will cause the doors to close.
Such an arrangement has not been entirely satisfactory for doors assembled from flat panels, stiles and rails, since a principal advantage of such doors is low cost due to commonality of parts. Thus, it is desirable to have top and bottom rails for both doors that are identical. It is also desirable to have corner connectors that are identical for all locations on the doors. For this reason it has been common to have symmetrical rails and corner connectors. Such symmetry usually requires use of spacers to provide lead-off for the doors.
One technique that has been employed for such panel doors employs a corner connector having two parallel holes into which either a pivot or guide can be inserted. This provides the appropriate lead-off, but some installation problems have been noticed.
The practice in this industry is to provide sets of hardware including stiles, rails, corner connectors, hinges, pivots and guides to assemblers. The assemblers acquire appropriate panels and assemble doors including such hardware. The doors are assembled without placing the pivots or guides in the holes in the corner connectors. Thus, the assembled doors are not "handed", that is, a pair of doors can be used in either the right or left side of a frame by inserting the pivots and guides into the appropriate holes. Surprisingly, a substantial number of mistakes are made by installers who place the guides and pivots in the wrong holes, resulting in doors that operate improperly. This can be corrected by rehanging the doors if noticed at the time of installation, however, it may require the installer to return, which is an unnecessary cost.
The problem of installers making mistakes in placing the pivots and guides in the wrong holes is not trivial. In one type of mirror door, corner blocks were adopted with two parallel holes in the block to recieve either a pivot or guide, as appropriate. A slot or pair of holes was provided in the rail so that both holes were exposed and the installer had to choose which hardware to put in each hole. Despite emphasis in instruction sheets of the importance of this choice, so many mistakes were made that this design was abandoned. It was replaced with a corner block having one symmetrically located hole and one hole was provided in each end of the rail. The installer couldn't make a mistake on the hardware spacing, but spacers are now needed to assure sufficient lead-off for the doors to operate properly.
In addition to the need for additional pieces of hardware and the narrowing of the door opening, it is desirable to use pivots and guides at different spacings from the edge of the door rather than spacers because the doors work better. The lead-off provided by placing the pivot further from edge than the guide gives smoother closing action than when lead-off is provided by spacers.
It is therefore desirable to provide hardware for bifold doors which is virtually foolproof for the installer so that errors in hanging the doors are almost automatically avoided. For economy it is important that the stiles, rails and corner connectors used in such hardware are identical to minimize costs of manufacture and inventory and to avoid mismatched sets of hardware.